Study: Premiums could rise 25 percent without insurance mandate

Premiums would rise because young, healthy people would be less likely to buy insurance. The purpose of the mandate is, in large part, to force healthy people into the system, offsetting the cost of guaranteeing coverage to people with pre-existing conditions.

If the healthcare law is implemented without a mandate, the paper says, fewer people would have private insurance than if the law had never been passed in the first place. The Medicaid expansion would be only slightly smaller without a mandate.

The insurance industry has filed a brief urging the Supreme Court to strike the entire healthcare law if it finds the mandate unconstitutional.